Candidates backed by Japanese Prime Minister Shinzo Abe's ruling bloc won two key governor elections on Sunday, setting the stage for him to push on with divisive policies to boost defence and restart nuclear reactors shut after the 2011 Fukushima disaster.

Incumbents backed by Abe's Liberal Democratic Party (LDP) and smaller coalition partner Komeito defeated opposition rivals in the northern prefecture of Hokkaido and in Oita in the south.

Elections including 10 gubernatorial polls, five races for mayors of major cities and 41 prefectural assemblies had been cast as a test for the prime minister's "Abenomics" recipe to revive the economy, the benefits of which critics say have not spread sufficiently to regions outside Tokyo.

Hokkaido and Oita were the only two governor races to pit candidates backed by Abe's camp against major opposition parties including the Democratic Party of Japan (DPJ), which was ousted by Abe's camp in 2012 after a troubled three-year reign.

The victories by Hokkaido Governor Harumi Takahashi and Oita Governor Katsusada Hirose halted a losing streak for Abe's bloc in local polls. Takahashi's main rival, Noriyuki Sato, had run on a platform that included opposition to nuclear power. Surveys show a majority of Japanese remain wary of restarting reactors.

Incumbents backed by the ruling bloc won the other eight races, six of them with DPJ support, media summaries showed.

"These elections had postponed Abe moving ahead on unpopular policies and now they've got the elections out of the way, he can move forward," said Jeffrey Kingston, director of Asian studies at Temple University's Japan campus. Elections in smaller municipalities will be held on April 26.

Voter interest was muted, which analysts said in part reflected opposition weakness. Turnout in the governor races was a record low 47.14 percent overall, Kyodo news agency said.

Opposition parties had trouble fielding candidates in many races, but an opposition candidate was elected mayor of Sapporo, the capital of Hokkaido. The LDP won a majority of total seats in prefectural assemblies for the first time in 24 years, media reported, but one in five candidates ran unopposed.

The government is likely to present bills to parliament next month to ease limits of the pacifist constitution on Japan's military, a drastic policy shift that many voters oppose.

Japan and the United States are hoping to reach a deal ahead of Abe's visit to Washington this month to add momentum to a 12-nation free trade pact, the Trans-Pacific Partnership (TPP). A loss in rural Hokkaido could have complicated those efforts.